Such jointing clamps are to be found in various forms. In their earliest forms, the outer sleeve of such clamps was made of porcelain and was normally provided with grip-enhancing flutes. The narrow end of the sleeve was closed, and at times had the form of a hexagonal screw-cap. Cable jointing clamps are primarily used to connect together single wires or multi-wire cables in junction boxes or wall terminal boxes of different kinds, either placed in wall or ceiling cavities or surface-mounted. When joining the wires, or conductors, together, the wire-ends are first bared and then spliced or bunched together, whereafter a jointing clamp is placed around the location of the joint and rotated a number of turns, whereupon through the combined agency of the internal screw-thread on the electrically conductive inner sleeve and also its conical configuration, firm electrical contact is established, both directly between the electrical conductors themselves and via the inner sleeve. By shaping the narrow end of the jointing clamp in the form of an hexagon, it was possible to tighten the clamp quickly and reliably, with the aid of a socket wrench or like tool.
At a later stage of development, the outer sleeves of such clamps were made of plastic, which were less bulky than the porcelain sleeves and enhabled the sleeves to be provided with "wings" or lugs in the manner of a wing nut, so as to enable the clamps to be assembled and tightened by hand, without the use of a tool.
However, there were many who considered such hand-assembly of the clamps unsatisfactory and wanting, and consequently tools were developed to fit the wings or lugs on the outer sleeve. These tools, however, resulted in such powerful tightening of the clamps that the ends of some of the wires or conductors in the wire-bunch embraced by the clamp were able to pass through the narrow end of the plastic outer sleeve, such as to represent a safety hazard. This, in turn, initiated the creation of several types of inner sleeves which were of complicated manufacture and the end parts of which were drawn together or otherwise closed, in order to prevent the wires from coming into contact with and passing through the outer sleeve.
At times it is necessary to carry out control checks or to search for faults in joints embraced by such jointing clamps, requiring an instrument or indicator to be connected to the cable joint insulated by the jointing clamp. With present day jointing clamps of this kind, it is necessary to dismantle the clamp by unscrewing the sleeves, carry out the check required and then reassemble the clamp. When this work is carried out a number of times, one or more of the wires in the cable joint are liable to break-off, causing the joint to be re-made.